1. Field of the Invention
This invention relates to a vibration switch, more particularly to a vibration switch with an electric contact body which is movable to engage or disengage from a contact member of a switching unit by means of a biasing member so as to place the switching unit in one of switch-on and switch-off states.
2. Description of the Related Art
Referring to FIG. 1, a conventional vibration switch 1, which is applied to a warning device or a step-counting device, is shown to include a metal swing shaft 101 which has a pivot end 102 mounted pivotally on a circuit board 105, and a swing end 103 with a metal head 104. A metal pad plate 106 is secured on the circuit board 105 adjacent to the head 104. A string-shaped biasing member 107 is connected to the swing shaft 101. When the switch is jerked by means of a force (F), the swing end 103 will swing to move the head 104 to punch the pad plate 106 so as to place the switch 1 in an on state. By virtue of the biasing action of the biasing member 107, the swing end 103 can swing back to remove the head 104 from the pad plate 106 so as to place the switch 1 in an off state. However, the swing shaft 101 is bulky, and has a relatively large number of components, thereby resulting in inconvenient carrying and packaging and manufacturing costs.
The object of the present invention is to provide a vibration switch which has a simple construction and compact size, and which can be fabricated at a relatively low cost.
According to this invention, the vibration switch includes a housing which is adapted to be mounted on a support in an upright direction. The housing has upper and lower inner wall surfaces which are spaced apart from each other in the upright direction, and a surrounding wall which is interposed between and which cooperates with the upper and lower inner wall surfaces to confine an accommodation chamber. An electric contact body is disposed in the accommodation chamber and is movable in the upright direction. The contact body has electrically conductive uppermost and lowermost ends opposite to each other in the upright direction. A biasing member has an engaging end which is disposed to engage one of the upper and lower inner wall surfaces, and a holding end which is disposed opposite to the engaging end and which holds the electric contact body such that the uppermost and lowermost ends are nearest to the upper and lower inner wall surfaces, respectively. By means of a biasing action against the weight of the electric contact body, the holding end restrains the electric contact body from moving towards the lower inner wall surface. A switching unit includes a contact member which is disposed to extend into the accommodation chamber such that the switching unit is placed in one of switch-on and switch-off states in response to movement of the electric contact body in the upright direction relative to the contact member as a result of an inertial force of the electric contact body when the housing is jerked to move upwards.